Even carbon number paraffin composition and method of manufacturing same

ABSTRACT

Paraffin compositions including mainly even carbon number paraffins, and a method for manufacturing the same, is disclosed herein. In one embodiment, the method involves contacting naturally occurring fatty acid/glycerides with hydrogen in a slurry bubble column reactor containing bimetallic catalysts with equivalent particle diameters from about 10 to about 400 micron. The even carbon number compositions are particularly useful as phase change material.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a Continuation of U.S. application Ser. No.13/742,991, filed Jan. 16, 2013, which is a Continuation of U.S.application Ser. No. 13/466,813, filed May 8, 2012, which is aDivisional of U.S. application Ser. No. 12/331,906, now U.S. Pat. No.8,231,804, filed Dec. 10, 2008, all of which are incorporated herein byreference, in their entireties, for any and all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to producing specialty materials andchemical intermediates from bio-renewable feedstocks such as animalfats, plant oils, algal oils, bio-derived greases, and tall oil fattyacid (hereafter referred to as biological feedstocks, or alternatively,fatty acids and/or glycerides depending upon the composition of thefeedstock). Specifically, the present invention relates to predominantlyeven carbon number paraffin compositions in the C₁₂-C₂₄ range, and thecatalytic hydrogenation/hydrogenolysis method used for its manufacture.

Paraffins in the C₁₂-C₂₄ range have useful applications as phase changematerial (PCM). The paraffins undergo solid-liquid phase transition inthe about −9° C. (15° F.) to about 50° C. (120° F.). Heat is absorbed asthe PCM paraffin melts and heat is released later when the PCM freezes.Fabricated systems that use PCM's as such are referred to as passivethermal storage devices. Due to relatively high latent heats ofsolid-liquid phase transition (referred to simply as latent heatshereafter), as well as compatibility with common material ofconstruction and high stability, paraffins are considered particularlywell-suited for PCM applications. Wall boards of a house impregnatedwith a PCM are an example of a passive thermal storage device. During ahot day, the PCM will absorb heat as it melts. Since there is notemperature change during phase transition, the surface in contact withthe thermal storage device stays at constant temperature until all PCMtherein has melted. The heat that would have made the house hot has thusbeen stored in the molten PCM. At night, as the temperatures get cooler,the molten PCM freezes and releases the heat thus preventing the homefrom getting cold. The melting-freezing cycles moderate the temperatureof the space enclosed within the passive thermal storage device despiteextreme night-day temperature swings outside. In general, PCMs are aneffective way of storing thermal energy (e.g. solar, off-peakelectricity, industrial waste heat), and reducing energy demand (e.g.for heating and air-conditioning).

The thermal storage capacity of the PCM is dictated by its latent heat.The higher the latent heat, the higher the thermal storage capacity ofthe PCM, and the smaller the required thermal storage device size/cost.

Table 1 provides the latent heats and melting points of paraffins. Asobserved therein, the latent heat for even carbon number paraffins ishigher than the la tent heat for odd carbon number paraffins of similartransition temperature. For example, n-heptadecane (carbon number 17)and n-octadecane (carbon number 18) melt in the 22-28° C. range. Whereasthe latent heat of n-heptadecane is 215 kJ/kg and the latent heat forn-octadecane is 245 kJ/kg or 14% higher. In general, the even carbonnumber paraffin heats of fusion in the C₁₄-C₂₄ range are 10-16% higherthan odd carbon number paraffins.

TABLE 1 Latent Heats and Solid-Liquid Transition Temperatures ofSelected Paraffins Carbon Melting Latent Name Number Point (° C.) Heat(kJ/kg) n-Tetradecane 14 4.5-5.6 231 n-Pentadecane 15 10 207n-Hexadecane 16 18.2 238 n-Heptadecane 17 22 215 n-Octadecane 18 28.2245 n-Nonadecane 19 31.9 222 n-Eicosane 20 37 247 n-Heneicosane 21 41215 n-Docosane 22 44 249 n-Tricosane 23 47 234 n-Tetracosane 24 51 255

In addition to PCM applications, even carbon number C₁₂-C₂₄ paraffinsare also used as chemical intermediates for linear alkyl benzene (C₁₂,C₁₄) and alkyenyl succinate (C₁₆, C₁₈), as well as lubricant/waxadditives.

2. Brief Description of the Related Art

The commercially practiced synthesis of even carbon number n-paraffinsinvolves ethylene oligomerization. Depending on the catalyst and reactoroperating conditions, this process produces a distribution of linearalpha olefins in the C₄ to C₂₀+ range. Linear alpha olefins in theC₄-_(C8) range are the main products of this process and are separated.These olefins are in high demand, mainly as comonomers for film-gradepolyethylene. The C₁₀+ even carbon number olefins are sold asintermediates for specialty chemicals, or hydrogenated to produce evencarbon number n-paraffins.

This ethylene oligomerization process for producing even carbon numberparaffins is highly dependent on crude oil and natural gas prices.Furthermore, n-paraffins have to be sold at a premium to the olefins tojustify the added cost of hydrogenating. These factors make the priceand availability of n-paraffins thus produced highly variable.

Another method of producing n-paraffins is Fischer-Tropsch synthesis.The liquid product of this reaction is a broad distribution of even andodd carbon number paraffins, from C₅ to C₅₀+.

Naturally occurring fatty acids and esters may be hydrotreated toproduce a hydrocarbon composition including even and odd carbon numberparaffins as reported in prior art, namely: Wong, et. al. “Technical andEconomic Aspects of Manufacturing Cetane-Enhanced Diesel Fuel fromCanola Oil”; Bio-Oils Symposium, Saskatoon, Saskatchewan, Canada; March1994. FIG. 2 of Wong et. al. includes typical gas chromatography/massspectrometry (GC/MS) trace of hydrotreated canola oil wherein therelative heights of even and odd carbon number paraffins are similar,indicating presence of comparable concentrations of each. The prior artmethod for converting triglycerides and fatty acids to paraffins employsa fixed-bed catalytic reactor, packed with commercially availablehydrotreating catalysts. These catalysts are cylindrical or three-flutedextrudates of alumina with nickel molybdenum or cobalt molybdenumsulfided metal activity. The typical equivalent diameter of thesecatalysts is from about 1.5 mm to about 2.0 mm.

The equivalent diameter is used to characterize non-spherical particlesby size. Equivalent particle diameter of a non-spherical particle isdefined as the diameter of a sphere having the same volume as thenon-spherical particle. For a cylindrical catalyst of diameter D andlength L, the equivalent particle diameter D_(p) is expressed asD_(p)=6(4/L+4/D)⁻¹. For a three-fluted extrudate, the equivalentparticle diameter expression is)

D _(p)=6[2/L+5π/(D(sin(60°)+1.25π)]⁻¹.

The fatty acid/glyceride feed is hydrogenated and deoxygenated in thefixed bed reactor packed with commercial hydrotreating catalysts. Asillustrated by Equations 1 and 2 for the example of triolein (oleic acidtriglyceride), the deoxygenation is achieved by oxygen hydrogenolysis,decarboxylation (removal of CO₂), and decarbonylation (loss of CO).

In both reactions, the glycerol backbone is converted to propane anddouble bonds are saturated. Since one carbon is removed from the fattyacids during decarboxylation and decarbonylation reactions (asillustrated in Equation 2), odd carbon number paraffins are formed fromeven carbon number naturally occurring fatty acids.

To this end, there is a need for even carbon number paraffincompositions and a selective process for producing even carbon numberparaffins. In particular, the present invention is a process forconverting biological feedstocks into even carbon number paraffincompositions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of an operation of acontinuous process in accordance with the present invention.

FIG. 2 is a schematic diagram of an embodiment of an operation of aseries-reactor process in accordance with the present invention.

FIG. 3 is a schematic diagram of an alternative embodiment of anoperation of a series-reactor process in accordance with the presentinvention.

FIG. 4 is a schematic diagram of an embodiment of an operation of abatch process in accordance with the present invention.

FIG. 5 is a bar graph summarizing the results of Example 1.

FIG. 6 is a bar graph summarizing the results of Example 2.

FIG. 7 is a McCabe-Thiele diagram for C₁₆-C₁₈ paraffin separation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to even carbon number paraffincompositions and a method for producing such even carbon number paraffincompositions from biological feedstocks. Paraffin compositions of thepresent invention have superior properties as phase PCM material.

It has been discovered that hydrocarbon compositions with very highconcentrations of even carbon number paraffins can be obtained frombiological feedstocks. The products are produced by a single-stephydrogenation/hydrogenolysis process of biological feedstocks. Oneembodiment of the process is carried out using a bimetallic catalyst ofabout 10 to about 500 micron equivalent particle diameter. The shorterdiffusion path length, more accessible pores, and lower intra-catalysttemperature gradients in the smaller catalyst system of the presentinvention reduce thermal decarboxylation and consequent co-production ofodd number paraffins.

One embodiment of the process of the present invention is preferablycarried out with the catalyst in the slurry phase. Commerciallyavailable catalyst extrudates may be ground and sieved to reduce thecatalyst size to the preferred range of the present invention, fromabout 10 microns to about 400 microns, most preferably from about 30microns to about 80 microns. Examples of the catalyst include but arenot limited to nickel-molybdenum (NiMo), cobalt-molybdenum (CoMo), ornickel-tungsten (NiW) on alumina or alumina phosphate supports.Pre-ground catalyst extrudates are commercially available in both oxideand active sulfide forms. The metal oxide catalysts are activated bysulfiding.

Commercial bimetallic catalysts are also available as slurry grades andwell-suited for the invention disclosed herein. Preferred examplesinclude sponge metal catalysts such as Mo promoted Raney® Ni and Co(Raney® is the trade name of the Grace Davison sponge metal catalyst).Sponge metal catalysts are formed by leaching nickel-aluminum orcobalt-aluminum alloys with concentrated caustic (sodium hydroxide)solution to form hydrogen active metal of high surface area. Theseslurry catalysts are active as received, but may be sulfided to achievethe desired selectivity.

Supported slurry catalysts suitable for the process of this inventionmay be prepared by impregnating spray-dried alumina or modified aluminasupports with solutions containing nickel, cobalt, molybdenum and/ortungsten compounds before calcining

It should be understood by one of ordinary skill in the art that anysuch catalyst may be utilized in the present invention so long as thecatalyst operates as described herein.

Referring now to the drawings and more particular to FIG. 1, showntherein is one embodiment of an operation of a process utilizing acontinuous flow reactor constructed in accordance with the presentinvention. A biological feedstock 101 is pressurized to reactor pressureof about 200 psig to about 2,000 psig via pump 102. Preferred operatingpressures for the slurry bubble column reactor are from about 400 toabout 1,000 psig. The feed 101 comprises of vegetable oils, animalfats/greases, plant oils, tall oil fatty acid, and algal oils. Algaloils can be naturally occurring or produced in bioreactors. Pressurizedliquid stream 103 enters a reactor 104.

The slurry reactor 104^(preferably a bubble column. The reactor catalyst loading is between about)1% and about 30% (dry bulk catalyst volume per total slurry volume),preferably between about 2% and about 20%. The catalyst particle size isfrom about 10 to about 400 microns, preferably from about 30 to about 80microns. The throughput of the pressurized biological feed stock 103, isbetween about 0.1 and about 10 LHSV (volume feed per volume catalyst perhour), preferably between about 0.5 and about 5 LHSV. These parametersset the slurry reactor 104 volume for the design feed rate.

The pressurized liqud stream 103 reacts therein with hydrogen 105 whichis optionally preheated through heater 116. The hydrogen-rich gas 105preferably has a hydrogen concentration between 70 and 100 mol %,preferably between 80 and 99 mol %. The hydrogen-rich gas 105 issupplied at a rate of about 3,000 to about 10,000 SCF/bbl (volume gasper volume biological feedstock). The gas to feedstock ratio ispreferably from about 4,000 SCF/bbl to about 8,000 SCF/bbl. The diameterof bubble column reactor vessel 104 is selected such that the gas flowrate is in the churn-turbulent regime from about 7 cm/s to about 40cm/s, preferably from about 8 cm/s to about 12 cm/s. A heatedhydrogen-rich gas 105A is dispersed through a sparger 119. The spargermay be of various configurations including but not limited to aring-type sparger with multiple orifices, a sintered metal plate orsintered metal distributing pipe(s) or co-fed with the biologicalfeedstock via a simple pipe distributor. In some embodiments thecatalyst is dispersed in the slurry phase by mechanical agitation. Thegas flow through the reactor 104 produces a uniform catalyst slurry 106.Alternatively, a side arm/downcomer (not shown) can also be deployed torecirculate de-gassed slurry to the reactor 104 which also aidescatalyst distribution in the reactor 104. The biological feedstockconverts into mainly even carbon number paraffins as it is dilutedwithin the catalyst-paraffin slurry 106.

The heat of reaction is in part removed by evaporation of a boiler feedwater 117 in cooling tubes/coils 120, producing steam 118. At thehydrodynamic regimes described herein, high heat removal may be achievedwith cooling coil device 120 immersed in the reactor 104. Typical heattransfer coefficient for a steam-generating cooling coil is in the 40 to200 Btu/hr-ft²-° F. range. The reactor temperature is thus controlledbetween about 450° F. (232° C.) to about 750° F. (399° C.), preferablybetween about 600° F. (315° C.) and about 650° F. (343° C.). At thesepreferred temperatures, high pressure steam (greater than about 400psig, and preferably greater than about 600 psig) may be produced andused for driving motors, generating electricity, and/or supplyingprocess heat.

The extent of back-mixing within the bubble column depends to a largeextent on the height-to-diameter ratio of the reactor. Typical columnshave successfully been modeled as 1.1-1.9 ideal CSTR's in series. At thepreferred reactor design conditions, the reactor liquid composition ismainly the paraffin, and the temperature very close to uniform.

The vapor product 107 from bubble column reactor 104 is cooled in aircooler 108 wherein byproduct water and light hydrocarbons condense. Atoperating pressures below 500 psig and temperatures above about 315° C.(600° F.), more than about 50% of the C₁₈-paraffin reaction product willvaporize and is condensed overhead with water and light hydrocarbons.

A three phase composition 109 is separated in separator drum 110. Thewater stream 111B and hydrocarbon 111A are thus separated from recyclehydrogen-rich gas 111C. In some embodiments, the hydrogen-rich gas 111Cmay be purified to remove some or all of the minor reaction byproductssuch as ammonia, hydrogen sulfide, and carbon oxides. Recyclehydrogen-rich gas may then be combined with makeup hydrogen to form thereactor hydrogen-rich gas 105.

The slurry 106 is transported through conduit 112 to filter 113 toseparate the catalyst from the reactor product. In some embodimentsfilter 113 is a cross-flow filter. In other embodiments, a hydrocyclonefollowed by a filter is used. It should be understood by one of ordinaryskill in the art that any device capable of separating suspended solidsfrom liquid may be used in the present invention. The catalyst slurryconcentrate stream 114 returns to reactor 104, while the filteredparaffin product 115 exits the reactor system. Product streams 115 and111B include equal to or greater than about 75 wt % even carbon numberparaffins in the C₁₂-C₂₄ range. Preferably, the product streams compriseof equal to or greater than about 80 wt % even carbon number paraffins.In some embodiments, the product stream may undergo further processingsuch as distillation to recover the even carbon number paraffinproducts.

In other embodiments of the present invention, a plurality of reactorsare employed to divide the hydrogenation/hydrogenolysis load over two ormore reactors. Those skilled in the art will recognize that thereactors-in-series configuration is used in back-mixed reactor systemsto achieve higher conversion at same or lower total reactor volume.

Referring now to FIG. 2, biological feedstock 201 is pressurized to thereactor system pressure in pump 202. The reactor system pressures are inthe same range previously specified herein. The reactor system furthercontains catalyst of type and size specified in the detailed descriptionof the invention. The pressurized feed 203 is optionally heated inheater 240. The preheated feed 203A enters the first stage reactor 204wherein partial conversion occurs in the catalyst slurry phase.Hydrogen-rich gas 205 is introduced into slurry bubble column reactor204 through a sparger device (not shown) at the rates previouslyspecified herein. Reactor 204 is equipped with cooling coils 210 tomaintain the reactor at the desired temperature range previouslyspecified. The extent of feed conversion in reactor 204 is about 10% toabout 90%, preferably about 30% to about 60%. Stream 206, the partiallyconverted product including paraffin, biological feedstock, and reactionintermediates such as fatty alcohols, fatty acids, and olefins, isfiltered through filter 207 to separate the catalyst. The catalyst richslurry 209 is returned to the reactor 204 while the filtered, partiallyconverted product 208 flows to second stage reactor 211.

Typically, a reactor 211 operates under the same temperature andgas-to-oil ratio as the reactor 204. In some embodiments the reactor 211operates at a higher temperature than the reactor 204. In someembodiments, the pressure in reactors 211 and 239 are lower than thereactor 204 to facilitate filtrate flow from the reactor 204 to thereactor 211, and from the reactor 211 to the reactor 239. Afterundergoing reaction with hydrogen provided by gas stream 212, apartially converted slurry 213 undergoes solid-liquid separation in afilter 214. A catalyst rich slurry 216 is returned to the reactor 211while the partially converted stream 215 is transferred to the reactor239. The total extent of feed conversion in the reactor 211 is about 30%to about 95%, preferably between about 50% and about 80%.

Hydrogen is supplied to the reactor 239 from the gas stream 217. Thetotal feed conversion achieved in this slurry bubble column reactor isbetween about 80% and about 100%, preferably at or very near about 100%feed conversion. The temperature, pressure, and gas-to-oil ratio are inthe same range described previously. Howver in some embodiments, thereactor 239 is operated at a higher temperature than the reactors 204and 211. A paraffin-catalyst slurry stream 218 is filtered in a filter219 to supply a product stream 221 and returning high-solids slurrystream 220 to the reactor 239. The product 221 includes equal to orgreater than about 75 wt % even carbon number paraffins in the C₁₂-C₂₄range. Preferably, the product stream 221 comprises of equal to orgreater than about 80 wt % even carbon number paraffins in the C₁₂-C₂₄range.

The off gas from the three slurry bubble column reactors in series,streams 222, 223 and 224, are combined to form a vapor stream 225. Thevapor stream 225 is cooled in a condenser 226 to a temperature fromabout 60° F. (15.5° C.) to about 160° F. (71° C.), preferably from about80° F. (27° C.) to about 140° F. (60° C.). A three phase stream 227enters drum 228 where the stream 227 is separated into a water phase229, a light hydrocarbon phase 230 and a gas phase 231. The gas phase231 is rich in hydrogen. The other components of the gas phase 231include propane, other light hydrocarbons, and minor byproductsdescribed previously. The hydrogen-rich gas stream may be partiallypurged (stream 232) with the rest recycled as stream 233. Theaforementioned impurities may be removed in a hydrogen purification unit234. The hydrogen purification unit 234 is typically a scrubber used toremove ammonia and hydrogen sulfide. A purified hydrogen-rich stream 235is then combined with makeup hydrogen 238 in recycle compressor 236. Arecompressed hydrogen-rich gas 237 is used to supply each of the slurrybubble column reactors.

In an alternative embodiment of an operation of a reactors-in-seriesprocess of the present invention, a slurry bubble column reactorcontaining catalyst of the type and size previously described herein maybe followed by a fixed-bed reactor. Referring to FIG. 3, the biologicalfeedstock 251 is pressurized by pump 252 to the reactor system pressurepreviously specified herein. The pressurized biological feedstock isheated by the reactor feed-effluent exchanger 254. A heated stream 255enters a slurry bubble column reactor 257 where a catalyst of the typeand size-range previously described herein is suspended in the slurryphase by sparging of hydrogen-rich gas 258. Reactor 257 is equipped withcooling coils 256 to control the temperature at target value within therange previously specified herein. A partially converted effluent slurry259 is processed through filter 260. A catalyst rich slurry 262 isreturned to the reactor 257 while a filtered partially converted product261 is transferred to a fixed-bed reactor 264 for achieving fullconversion. Before entering the reactor 264, the liquid feed is mixedwith optionally preheated hydrogen 286. A combined feed 263 tricklesthrough the fixed-bed reactor 264 wherein the partially convertedfeedstock and reaction intermediates are fully converted to apredominately even carbon number paraffin composition. The fixed-bedreactor 264 is operated adiabatically and the temperature is allowed torise within the preferred range previously specified herein. A reactoreffluent 265 is partially cooled in exchanger 254. A partially cooledproduct 266 enters high pressure separator 267 wherein the hydrogen-richvapor stream 270 is separated from a mainly even carbon numberparaffinic liquid product 268. The liquid product 268 may be furtherprocessed through distillation to recover the desired even carbon numberparaffin composition previously specified herein.

The hydrogen-rich gas streams 270 and 269, from the high pressureseparator 267 and the slurry bubble column reactor 257 respectively, arecombined to form vapor stream 271. Water 271A is added to vapor stream271 to wash any deposits that may form upon condensation in a condenser272. A cooled stream 273 is a three phase composition which is separatedin drum 274. The liquid fractions include byproduct water 275 and lighthydrocarbons 276. A hydrogen-rich gas 277 is partially purged as stream278. The rest of the gas, stream 279 is optionally treated inpurification unit 290 to remove ammonia, hydrogen sulfide, and otherbyproducts of the hydrogenation/hydrogenolysis reaction. A purifiedhydrogen-rich gas 280 is combined with makeup hydrogen 282 in recyclecompressor 281. A recompressed hydrogen-rich gas 283 is optionallyheated in heater 284 before supplying the slurry bubble column 257 andthe fixed-bed reactor 264.

The slurry catalyst reaction may also be conducted in batch mode. Thismay be a preferable embodiment when large volume production is notsought, or when the paraffin products from different feed stocks need tobe segregated.

Referring to FIG. 4, a biological feedstock 301 is charged to a batchstirred reactor 302. The reactor 302 is equipped with an agitatorassembly 303 for suspending solids and dispersing gas, and a jacket 304for heat transfer. A slurry catalyst 306 is then added to the reactor302. The catalyst is of the type and size-range previously describedherein. The reactor is then purged and pressurized with hydrogen 307 tothe target operating pressure. Pressure ranges described previously forthe continuous flow reactor embodiments are applicable to the batchreactor embodiment as well. These preferred pressures are from about 400psig to about 1,000 psig.

The reactor 302 is then heated to a target operating temperature in therange previously described for the continuous reactor embodiments,preferably between 450° F. (232° C.) and 650° F. (343° C.). Theoperating temperatures may be achieved by circulation of a heat transferfluid 308 through the reactor jacket 304. Once at target temperature,the heat transfer fluid 308 is used for cooling. The hydrogen 307 supplyrate is used to limit the release of reaction heat through a temperaturecontrol loop 309. In some embodiments, the hydrogen flow rate ismaintained constant and the reactor pressure is controlled through aback pressure control loop 310, while temperature is controlled throughcirculation rate of the heat transfer fluid. In some embodiments,reactor 302 is equipped with a cooling coil (not shown) to increase heatremoval and shorten batch cycle.

The batch reactor is equipped with piping 312, 312A, and condenser 318.Condensable byproducts of the hydrogenation/hydrogenolysis reactionwhich occurred in reactor 302, light hydrocarbons and water, are thuscollected in drum 314 after cool-down with coolant 316 in condenser 318.Upon completion of the reaction, when no more H₂ consumption isobserved, the reactor 302 is cooled to about 140° F. (60° C.) to about160° F. (71° C.) and the products and byproducts are drained out throughconduits 320 (water, followed by light hydrocarbons) and 322 (mainparaffin product). Most of the catalyst settles to the bottom of reactor302 after agitation has been turned off, for reuse in the next batch.The suspended catalyst fines are removed from the n-paraffin productthrough filter 324. Sintered metal or cartridge elements may be used forcatalyst filter 324. A filtered product 326 has the same even carbonnumber paraffin composition previously described in the continuous flowreactor embodiments of the present invention.

In order to further illustrate the present invention, the followingexamples are given. However, it is to be understood that the examplesare for illustrative purposes and are not to be construed as limitingthe scope of the subject invention.

EXAMPLES Example 1 Hydrogenation/Hydrogenolysis of Canola Oil with 1/16″Trilobe Catalyst Extrudates (D_(p)˜1.2 mm) in a Fixed-Bed Reactor

The present example demonstrates the conversion of a biologicalfeedstock, canola oils, into paraffinic compositions using standard-sizecatalyst extrudates. A 100 cc isothermal tubular reactor was filled with80 cc of a commercially available NiMo catalyst (purchased from CatalystTrading Corporation, Houston, Tex.) of 1.2 mm equivalent particlediameter, and 70-100 mesh glass beads. The catalyst was sulfided in thepresence of hydrogen with dimethyl disulfide at two hold temperatures: 6hours at 400° F. and 12 hrs at 650° F. Hydrogen sulfide break-throughwas confirmed before the temperature was raised from 400° F. (204° C.)to 650° F. (343° C.) at 50° F/hr. After sulfiding, the reactor wascooled to 400° F. (204° C.).

Next a fatty triglyceride feed was introduced to the isothermal reactor.The reactor was slowly heated to 650° F. to achieve full conversion ofthe triglyceride feed to a paraffin composition. The reactor temperaturewas further increased to 700° F. (371° C.) to maintain good catalystactivity at 80 cc/hr feed rate (1.0 hr⁻¹ LHSV). Canola oil feedstock wasthen introduced at these reactor conditions.

The product was analyzed using a gas chromatography (GC) methodinvolving calibration with n-paraffin standards. The results of feedconversion to paraffins are summarized in FIG. 5. As observed therein, asignificant percent of C₁₇ paraffins was produced fromdecarbonylation/decarboxylation of C₁₈ fatty acids. The overallconcentration of even carbon number paraffins was only 61 wt %.

Example 2 Hydrogenation/Hydrogenolysis of Canola Oil with Crushed andSieved Catalyst (D_(p)=30-80 micron) in Slurry Reactor

The catalyst used in Example 1 was discharged from the reactor, crushed,and sieved into a 30-80 micron particle-size cut. Ten (10) grams of the30-80 micron cut of the ground catalyst was combined with 300 g ofcanola oil in a 1 liter Autoclave stirred-reactor. The agitation was setat 1000 rpm. The reactor was purged with N₂ before starting H₂ flow at 3L/min. The reactor was controlled at 500 psig pressure. The temperaturewas ramped at 1° F./min to hold temperatures of 450° F. (232° C.), 500°F. (260° C.), 550° F. (288° C.), and 600° F. (316° C.). Liquid sampleswere obtained at each hold temperature and analyzed by GC. The holdtimes were 20 hrs at 450° F. (232° C.), 5 hrs at 500° F. (260° C.), 23hrs at 550° F. (288° C.), and 19 hrs at 600° F. (316° C.).

The results of the slurry catalyst conversion reaction are summarized inFIG. 6. It is thus observed that most of the C₁₈ and C₁₆ fatty acids inthe canola oil were converted to C₁₈ and C₁₆ paraffins, suggesting ahigh selectivity for the oxygen hydrogenolysis mechanism and lowdecarboxylation/decarbonylation. The overall concentration of evencarbon number paraffins was 80 wt %.

Example 3 Even Carbon Number Paraffin Composition from Rapeseed Oil

Rapeseed oil was the third largest source of vegetable oil in the world(USDA year 2000 statistics), behind palm and soybean oils. The oil yieldfrom rapeseed is 40-50%, compared to only 20 percent for soybeans. Table2 summarizes the fatty acid profile of representative biologicalfeedstocks.

TABLE 2 Fatty Acid Composition of Several Common BiologicalFeedstocks⁽¹⁻⁵⁾ Saturated Acids Mono-Unsaturated Acids Poly-UnsaturatedEicosenic/ Eicosenic/ Acids Caprylic Capric Lauric Myristic PalmiticStearic Behenic Palmeic Oleic Beheneic Linoleic Linolenic C8:0 C10:0C12:0 C14:0 C16:0 C18:0 C20:0/C22:0 C16:1 C18:1 C20:1/C22:1 C18:2 C18:3wt % wt % wt % wt % wt % wt % wt % wt % wt % wt % wt % wt % Animal fatsChicken Fat — — — — 7 2 — — 69 — 17 — Beef Tallow — —   0.2 2-3 24-3021-26 0.4-1   — 39-43 0.3 2-3 1 Yellow Grease — 3 3  1-11 23-27 10-12 —1   29-50 —  2-15 1 Choice White — 7 3 9   25  12  — — 27 — 1-3 1 GreaseLard (pork fat) — — — 1-2 25-30 12-16 — 2-5 41-51 2-3  4-22   0.2Vegetable Oils Soybean Oil — — — 0.3  7-11 3-6  5-10 0-1 22-34 — 50-60 2-10 Corn Oil — — — 0-2  8-11 1-4 — 1-2 28-50 0-2 34-58 1 CottonseedOil — — — 0-3 17-23 1-3 — — 23-41 2-3 34-55 1 Canola Oil — — — — 4 2 — —62 — 22 10  Coconut Oil 5-9 4-10 44-51 13-18  7-10 1-4 — — 5-8 — 1-3 —Sunflower Oil — — — — 6-7 4-5 1.4 — 19 68-69 0.3-1   Palm Oil — — — 1-632-47 1-6 — — 40-52 —  2-11 — Palm Kernel Oil 2-4 3-7  45-52 14-19 6-91-3 1-2 0-1 10-18 — 1-2 — Rapeseed — — — — 2-5 1-2 0.9 0.2 10-15 50-8010-20  5-10 (High Eurcic)⁽¹⁾http://www.scientificpsychic.com/fitness/fattyacids.html ⁽²⁾Kinast,J. A. March 2003, “Production of Biodiesel from Multiple Feedstocks andProperties of Biodiesel/Diesel Blends, NREL/AR-510-31460 ⁽³⁾Tyson, K.S., NREL Presentation “Biodiesel for New England” Mar. 26, 2003 ⁽⁴⁾FoodFats and Oils, Institute of Shortening and Edible Oils, Ninth Edition2006 ⁽⁵⁾a “—” in a cell means that this constituent is not present

As observed therein, rapeseed oil consists of 50-60 wt % C₂₂ fatty acidswith the balance mainly C₁₈ fatty acids. According to the inventiveconversion process disclosed herein, rapeseed oil will produce an evencarbon number composition comprising of a ratio of about 1:1 to 1.5:1C₂₂:C₁₈ n-paraffins. This composition is useful as a PCM in constructionor textile/clothing application for high temperatures, including desertclimates when day times can surpass 44° C. (melt point of C₂₂ paraffin),and night times below 28° C. (freeze point of C₁₈ paraffin). The hightemperature phase transition makes this PCM composition well suited forcomputer cooling applications (i.e. heat sink or cooling pad under thecomputer) as well.

Example 4 Even Carbon Number Paraffin Compositions from Palm Oil andPalm Kernel Oil

Palm oil recently surpassed soybean oil as the largest volume plant oilproduced in the world. Whereas palm oil itself is derived from the fruitof the palm tree, the palm kernel oil is extracted from the fruit'sseeds. Referring to Table 2, palm oil consists of about 40 wt % C₁₆fatty acids, with the balance mainly C₁₈ fatty acids. According to themethod of the present invention, the palm oil is converted to a mainlyeven carbon number paraffin composition in the C₁₆-C₁₈ range withC₁₈:C₁₆ weight ratio of about 1.5:1. The composition is useful as a PCMfor construction and textile/clothing applications in the 18° C. to 28°C. range.

Referring to Table 2, palm kernel oil has a fatty acid composition ofabout 45-52 wt % C₁₂, 14-19 wt % C₁₄, 6-9 wt % C₁₆, and 11-17 wt % C₁₈.According to the present invention, the biological feedstock isconverted to a mainly even carbon number n-paraffin compositionincluding C₁₂, C₁₄, C₁₆, and C₁₈ components. The n-paraffin compositionmay be distilled to yield a C₁₂/C₁₄ composition suitable for very lowtemperature PCM applications (such as for bridge warmers and divesuites) or as chemical intermediates (such as for producing linear alkylbenzenes).

Example 5 Separation of Even Carbon Number Paraffins Derived from theMethod of the Present Invention

The method of the present invention may be used to convert most animalfats into a composition with approximately 30 mol % C₁₆ n-paraffins andthe balance mainly C₁₈ paraffin. Vacuum distillation is a wellunderstood and broadly practiced separation technology. At 20 torrpressure, the vapor-liquid equilibrium (VLE) constants (“K-values”) forn-octadecane and n-hexadecane are 1.34 and 0.82 respectively (computedusing HYSYS simulation software's Peng-Robinson thermodynamic model).These K-values may be used to generate the equilibrium curve of FIG. 7.Distillation column operating lines have been added according to theMcCabe-Thiele methodology as disclosed in prior art, namely, Foust et.al. Principles of Unit Operations, 2^(nd) Ed.; John Wiley & Sons: NewYork, 1980; Chapter 7. According to McCabe-Thiele procedure fordistillation column design, with a reflux ratio of 6.5, or 30% higherthan minimum reflux, a separation yielding 90 mol % purity C₁₈ and C₁₆n-paraffin products requires 14.5 theoretical stages. Assuming 73% trayefficiency, the vacuum tower requires 20 actual trays.

While the C₁₈ product of the separation can be sold as a PCM for narrowtemperature control applications, the C₁₆ n-paraffin (n-hexadecane orcetane) has other markets. One large volume application is diesel fueladditive. Another use of linear C₁₆ hydrocarbons is as intermediates forspecialty chemicals including alkenyl succinates for paper coatings.

The analysis of this example shows that the even carbon numbercompositions of the present invention, such as those derived from animalfats/greases, are well suited for producing chemicals using conventionalseparation techniques.

While the compositions and methods of this invention have been describedin terms of preferred embodiments, it will be apparent to those of skillin the art that variations may be applied to the process describedherein without departing from the concept and scope of the invention.All such similar substitutes and modifications apparent to those skilledin the art are deemed to be within the scope and concept of theinvention as it is set out in the following claims.

What is claimed is:
 1. A phase change material composition comprising atleast 75 wt % even carbon number paraffins, wherein the paraffins areproduced by hydrogenation/hydrogenolysis of naturally occurring fattyacids and esters.
 2. The composition of claim 1 comprises at least 80 wt% even carbon number paraffins
 3. The composition of claim 1 wherein theeven carbon number paraffins comprise n-hexadecane and n-octadecane. 4.The composition of claim 1 wherein the even carbon number paraffinscomprise n-octadecane and n-docosane.
 5. The composition of claim 1wherein the even carbon number paraffins comprise n-dodecane andn-tetradecane.
 6. The composition of claim 1 wherein the composition isused in thermal storage devices.
 7. The composition of claim 1 whereinthe composition is used as feedstock to produce even carbon numbern-paraffin products.
 8. The composition of claim 1 wherein thehydrogenation/hydrogenolysis occurs in the presence of a catalystcontaining nickel, molybdenum, cobalt, and/or tungsten.
 9. Thecomposition of claim 8 wherein the catalyst has an equivalent diameterof about 400 microns or less.
 10. The composition of claim 8 wherein thecatalyst has an equivalent diameter of about 80 micron or less.
 11. Thecomposition of claim 10 wherein the hydrogenation/hydrogenolysis occursin slurry phase.